The present invention relates to a method for the formation of metallic-organo-peroxides and organo-metallic peroxides and to such compounds so produced.
Many methods for forming organo-peroxides are known. Reference is made to the book, "Hydrogen Peroxide in Organic Chemistry" by John G. Wallace, published by the Electro Chemical Department of E. I. du Pont De Nemours and Company.
Generally, an organic peroxide is defined as a derivative formed by replacing one or both hydrogen atoms of hydrogen peroxide by an organic radical. The present method produces compounds which include a metal atom bonded to an organic radical and a peroxide type group bonded to the organic radical. The peroxide group is of the oxygen to oxygen type bond in which a hydrogen atom can be connected to one of the oxygen atoms. The method of the present invention also produces a product wherein the organic radical has a metallic atom bonded to it and the peroxide group is bonded to the metal atom. The differences in the types of products produced gives rise to the distinction between the description of the product as being on the one hand, a metallic-organo-peroxide and on the other hand, an organo-metallic-peroxides.
One elementary method of producing an organic peroxide makes use of the fact that a strong aliphatic acid solution with hydrogen peroxide exists in equilibrium with the corresponding organic peracid. ##EQU1##
However, in the absence of a strong acid catalyst, such as a mineral acid, the attainment of equilibrium is impractically slow, especially at temperatures below 40.degree.C. At higher temperatures, it is difficult to prevent the excessive loss of active oxygen unless the oxidizable organic substance is also present to react with the organic peracid as it forms. For this reason, it is common practice, whenever possible, to employ hydrogen peroxide under conditions for the in situ formation of the organic peracid at temperatures ranging up to the boiling point of the aliphatic acid.
The peracid formed in situ can be reacted with an olefinic material to produce an epoxy (oxirane) compound as a primary product. ##EQU2##
The reaction, is, of course, two-staged, since the peracid must be formed first.
Common organic peracid systems include glacial acetic acid or formic acid with hydrogen peroxide. The organic peracids thus formed are unstable and considered a hazard particularly when the organic peracid is relatively concentrated.
It is known that the mild oxidizing action of hydrogen peroxide is increased considerably by use of certain metallic catalysts. One example of a metallic catalyst is ferrous sulfate which is employed in a redox system: EQU Fe.sup.+ .sup.+ - Fe.sup.+.sup.+.sup.+
it has been employed with hydrogen peroxide and is generally known as Fenton's Reagent. Other catalysts include osmium and tungstic oxides employed to hydroxylate aromatic and unsaturated hydrocarbons and to effect other oxidations. These additional catalysts are classed as Milas' Reagents which together with Fenton's Reagent constitute the bulk of the metal activated hydrogen peroxide systems. Hydrogen peroxide in metal-activated systems reacts as though it was dissociating into two hydroxyl radicals.
Fenton's oxidations are, in fact, believed to proceed through the intermediate formation of hydroxyl free radicals: EQU Fe.sup.+.sup.++H.sub.2 O.sub.2 .fwdarw.Fe.sup.+.sup.+.sup.++OH.sup.-+OH
the Fe.sup.+.sup.+-F.sup.+.sup.+.sup.+ system, and such other redox systems as Cu.sup.+ - Cu.sup.+.sup.+, are normally employed with hydrogen peroxide in aqueous acid medium. A small amount of sulfuric acid is added to an aqueous solution of ferrous sulfate heptahydrate so that Fenton's oxidations are carried out at a pH of. 1-4. In a less acid solution, the reaction efficiency is decreased, and hydrogen peroxide is catalytically decomposed.
Other metal-activated systems include in decreasing order of catalytic efficiency the following: EQU O.sub.s O.sub.4, WO.sub.3, MoO.sub.3, SeO.sub.2, CrO.sub.3, V.sub.2 O.sub.5, TiO.sub.2 and Ta.sub.2 O.sub.s
Derivatives of the aforementioned catalyst, such as phosphotungstic acids (e.g. H.sub.3 PO.sub.4 12WO.sub.3) are also effective as catalysts for hydrogen peroxide.
The prior art shows four general methods of incorporating the peroxide bond (--OO--) into organic molecules. These methods include auto-oxidation, ozonization, the association of oxygenated free radicals, and the addition and substitution reactions of hydrogen peroxide and hydroperoxides. Typically, hydrogen peroxide is related with acids, anhydrides, esters, alcohols, organic sulfates and sulfonates, carbonyl compounds, and organic chlorine compounds to produce organic peroxides.
The reactions of acids anhydrides and esters with hydrogen peroxide ordinarily lead to the formation of organic peracids, although other organic percompounds may result. The most popular method of preparing a peracid is by mixing hydrogen peroxide and an aliphatic acid in the presence of a strong acid catalyst such as sulfuric acid. Typically an equimolar mixture of high strength hydrogen peroxide and acetic acid with one percent sulfuric acid catalyst reaches equilibrium after standing for 12 to 16 hours.
The resin technique for peracetic acid formation is considered much faster and permits continuous or batchwise preparation.
The resin technique or peracetic acid formation is operated simply by passing a mixture of glacial acetic acid and hydrogen peroxide through a cation exchange resin column. The column contains polystyrene sulfonic acid resin which has been treated with glacial acetic acid to remove excess water. Under conditions for operation of the resin technique, a contact time of 12 to 16 minutes at about 45.degree.C is sufficient for maximum conversion of hydrogen peroxide to peracetic acid. The serious drawback in this method is that it requires high strength hydrogen peroxide and thus creates a serious hazard.
A common procedure for converting an alcohol, R-O-H, to a hydroperoxide, R-OOH, consists of reacting hydrogen peroxide and tertiary alcohols in strong sulfuric acid. The reaction is believed to involve the formation of an intermediate sulfate and, therefore, is similar to the alkylation of hydrogen peroxide by dialkyl sulfates. The reaction often results in serious explosions, although the final products of such reactions are relatively stable. Prior art methods do not produce peroxide products with primary or secondary alcohols very easily. Mixtures of a tertiary alcohol and hydrogen peroxide have been used as germicides, fungicides, bleaching agents, and peroxide reagents.
The strong sulfuric acid used in the hydrogen peroxide - alcohol reaction is sometimes replaced by heteropolyacids having multiple inorganic acid radicals. The heteropolyacids which are soluble in ether, contain the elements of phosphorus, silicon, or boron, coordinated with a metallic oxide such as tungsten oxide. The characteristic solubility of heteropolyacids allows the preparation of alkyl hydroperoxides to be carried out in ether.
The known methods of converting carbinols of many types to hydroperoxides and disubstituted peroxides makes use of strong sulfuric acid as a catalyst. Typically, acetylene peroxides are formed by the interaction of hydrogen peroxide and the hydroxyl group of acetylenic carbinols in the presence of strong sulfuric acid. The peroxides thus formed are unusually stable despite the presence of the acetylenic bond.
Dialkyl sulfates and alkyl hydrogen sulfates can be used to produce hydroperoxides and dialkyl peroxides by a reaction with alkaline hydrogen peroxide. These peroxides are often used as polymerization catalysts and diesel fuel additives. Typically, primary and secondary dialkyl peroxides are prepared by the alkylation of hydrogen peroxide with alkyl methane sulfonates in liquid alkaline methanolic solution. A known method for producing sodium peroxy sulfonates is carried out by reacting a sulfonic acid such as naphthalene sulfonic acid and sodium peroxide in a liquid medium. The operation is conducted in a cold environment to reduce the violence of the reaction. The peroxy product obtained has approximately 6% active oxygen and is considered useful as a bleaching agent or insecticide.
Olefins have been transformed to hydroperoxides in a reaction which amounts to the addition of hydrogen peroxide to the double bond. The reaction, however, is conducted in strong sulfuric acid according to known methods and probably involves the formation of an intermediate sulfate. ##EQU3##
The preparation typically takes place at below 0.degree.C and takes several hours.
It is known that hydrogen peroxide can be reacted with an aldehyde or a ketone in the presence of a catalyst to form a peroxide compound. The following equilibrium is believed to occur for an aldehyde and hydrogen peroxide: ##EQU4##
Typically, formaldehyde is treated with hydrogen peroxide in ether in the presence of P.sub.2 O.sub.5. The peroxide product is very explosive. Both cyclic ketones and aliphatic ketones have a tendency to form stable but hazardous peroxides. As a rule, known methods produce unstable peroxides of aromatic ketones and aromatic aldehydes because of the greater ease of migration of the phenyl radicals attached to the carbonyl carbon.
It is known that organic peroxides can be formed by reacting hydrogen peroxide with organic chlorine compounds. The reaction is generally conducted in the presence of a chlorine acceptor which may be caustic or organic bases such as pyridine.